It is often desirable to have computer models of large physical structures, such as a petroleum refinery. Computer models facilitate an understanding of the structure that is beneficial in a number of ways. One technique for constructing these computer models is to use a laser scanning system such as the system described in U.S. patent application Ser. No. 09/177,913. (The '913 application is a continuation of Ser. No. 08/638,961 which, in turn, is a continuation of International Application No. PCT/US97/06793. Application '06793 has International Publication No. WO 97/40342.)
The '913 system includes a combination laser scanner and PC software system that measures, visualizes and models large structures and sites with high speed, high accuracy and over a large range. In use, the device is oriented towards the scene and the user selects the desired measurement area and measurement point spacing. A detailed 3-D geometry of exposed surfaces is remotely captured in the form of a dense, accurate, three dimensional point cloud.
The '913 system includes a passively Q-switched pulsed laser. The laser beam is scanned over the target using computer-controlled galvo scanning mirrors. The system includes a video monitor for capturing the scene and displaying it on a computer such as a laptop. Using this video image, the operator can select the area to be scanned by the laser.
The galvo mirrors direct the laser through repeated vertical scans, moving over horizontally after each vertical scan. By accurately monitoring the time of flight of each laser pulse out from the device and back into the device, exact positional information of the target can be calculated.
Each measured point has associated with its 3-D information in the point cloud. The system software can display the point cloud to the user. As discussed herein in greater detail, the point cloud can be used to directly carry out a number of procedures. In addition, the system can process the point clouds into wire meshes, 3-D models and 2-D drawings for export to popular computer-aided design (CAD) rendering or other software.
In the '913 application, some basic real-world examples were discussed. For example, it was suggested that the system could be used to create a three dimensional image of a construction site or a building. This 3-D data could be viewed directly or used to generate CAD drawings.
Because of the high speed and accuracy of the system, further applications have been developed which can greatly benefit from these features. This patent application is intended to describe some of these concepts.